Alex may head north to Texas or Louisiana

Tropical Depression Alex has held together fairly well during its passage over Mexico's Yucatan Peninsula, and stands poised to re-intensify back into a tropical storm once it emerges from the coast tonight. Alex brought heavy rains to northern Honduras, Mexico's Yucatan Peninsula, and Belize over the weekend. It was not a good beach day in Cozumel yesterday, as 9.25" of rain fell. Cancun received 2.05" over the weekend, and Belize City received 4.57". Satellite loops show that Alex's heavy thunderstorms are mostly gone near the center, though there are some impressive bands of precipitation well away from the center. There is an upper-level high pressure system a few hundred miles west of Alex, and the clockwise flow air around this high is bringing upper-level winds out of the northwest of about 5 knots over the storm, contributing to the 5 knots of wind shear observed in this afternoon's wind shear analysis from the University of Wisconsin's CIMSS group. Sea Surface Temperatures are very warm, 29 - 30°C, and dry air is currently not a problem for Alex.

Figure 1. Afternoon satellite image of Alex.

Forecast for Alex: which model should you trust?While the track forecast for Alex today through Monday is fairly well-assured, the longer range forecast has become highly uncertain. An increasing number of our reliable models are now indicating Alex may take a more northerly track beginning on Tuesday, with possible landfall on the Texas coast near Galveston on Friday (according to the 8am run of the GFS model) or into western Louisiana on Wednesday (the 8am run of the Canadian model.) The key question remains how Alex will react to the trough of low pressure expected to swing down over the Eastern U.S. on Monday and Tuesday. Most of the models were predicting that the trough would not be strong enough to swing Alex to the north, and several of them continue to predict this. The 8am runs of the NOGAPS and ECMWF models, for example, take Alex into the Gulf coast of Mexico 150 miles south of Texas, on Wednesday. The GFDL and HWRF models split the difference, with the GFDL predicting a Thursday landfall in southern Texas near Brownsville, and the HWRF predicting a Thursday landfall near Corpus Christi. Morris Bender of the GFDL group has just provided me the track forecast from an improved experimental version of the GFDL that shows landfall between Corpus Christi and Galveston. So which model should you trust? Last year, the best performing models at the 3 - 4 day forecast range were the GFS and the Canadian, and these are the models that are currently calling for the more northerly track towards the upper Texas coast and Louisiana. Residents of those areas should review their hurricane preparedness plans and anticipate that Alex could make landfall as early as Wednesday in their vicinity. Residents of the Mexican coast south of Brownsville should make similar plans, as Alex could just as easily hit there.

Re-intensification of Alex is likely once the center of Alex moves offshore, though this will initially be slow due to the current disorganized state of the storm and the relatively low total ocean heat content in the 100-mile-wide stretch of water on the west side of the Yucatan Peninsula. Once Alex moves more than 100 miles from the Yucatan, total heat content of the ocean increases substantially, and Alex will have the opportunity to intensify significantly. A longer time spent over water will give Alex more of a chance to strengthen, and it is possible Alex could intensify into a major hurricane if landfall is delayed until Thursday or Friday. However, Alex's intensification may be limited the farther north it gets, as water vapor satellite images show plenty of dry air over Texas that might interfere with development. Wind shear might also be an issue for Alex if it pushes far enough north, and a slow-moving storm tends to pull up cold water from the depths, limiting intensification. In short, Alex has the potential to intensify into a major hurricane, but there are plenty of roadblocks that make this only a 10% probability in my estimation.

I was wondering maybe they are waiting to make sure it can push the ridge out before scaring everyone..altho..the earlier they change it..the earlier everyone else knows...they must think it wont push it enough.

Quoting Levi32:Impressive pressure falls going on as Alex's center moves over the west coast of the Yucatan....very distinguished for a system that just spent the better part of a day over land and was only a borderline TS/hurricane at landfall.

I didn't expect the pressure to remain sub-1000mb.

If those are coming from Mexican Weather stations, double check it. Last night one had a pressure of 977mb.

That is interesting because it would appear that the oil spill area has not heated up more than the rest of the gulf, as some had expected.

What do you expect when you have supercooled oil boiling up to the surface. Temperatures at the bottom of the gulf are near or below 32 degrees, it would have some effect, and the oil sheen increases the amount of light reflected, a black patch of oil would heat in the sun, but the sheen is like a mirror as long as the winds are calm like they were about this time last year when I sailed from New Orleans to Mexico it was like a sheet of glass. Calmest gulf crossing I ever had the pleasure of vacationing on.

Impressive pressure falls going on as Alex's center moves over the west coast of the Yucatan....very distinguished for a system that just spent the better part of a day over land and was only a borderline TS/hurricane at landfall.

Quoting southlouisiana:What is the "ensemble models"? I can find no definition of it and it makes no logical sense to me.

Ensemble models are run at a lower resolution and with different initial conditions than the parent model such as the GFS. The different initial conditions are an attempt to account for uncertainty since you can't capture an instantaneous snapshot of the atmosphere globally.

If Alex takes a path similiar to Brett in 1999 hopefully it can strike a less populated area of Texas.Although the bigger size of Alex the effects will be felt further away. Brett was a Cat 4 at landfall.

satellite images show that alex continues to have a large and well-defined circulation with plenty of banding features. near the center...however...convection has decreased...probably due to the influence of land. the mexican navy surface station at isla perez recently reported 30 kt winds...so the initial wind speed is kept at 30 kt. an air force reserve hurricane hunter aircraft is scheduled to investigate alex this evening after the center moves offshore.

the initial motion of alex is a little slower...with a 12-hr average yielding an estimate of 300/8. the pivotal question for the long-term forecast track of the tropical cyclone appears to hinge on the strength of mid-level ridging over the northern gulf coast. the models that show a weaker ridge...such as the cmc/gfs/hwrf... allow the tropical cyclone to turn toward the north-northwest and north and approach the northwestern gulf coast in several days. other models...such as the ecmwf/ukmet/nogaps...have a stronger ridge and keep alex moving to the northwest or west-northwest into mexico. overall the model guidance has shifted slightly to the north...and the official forecast is a little to the right of the previous one. since there is considerable model spread...this track forecast is thought to be of below-average confidence.

while there is a large disagreement on the track of alex...the global models are in much better agreement with the large-scale environment. these models show an upper-ridge axis sitting very near the tropical cyclone for the next several days...in a favorable position for intensification. combined with the warm waters of the gulf of mexico...strengthening is likely...especially after alex moves farther away from the yucatan peninsula. given the overall environmental conditions...it is surprising that the gfdl/hwrf do not show more intensification...leaving the system as a tropical storm for many days. the statistical guidance seems more reasonable and the nhc forecast is close to the ships model...and is not too dissimilar from the previous forecast.

TROPICAL DEPRESSION CENTER LOCATED NEAR 19.2N 90.9W AT 27/2100ZPOSITION ACCURATE WITHIN 20 NM

PRESENT MOVEMENT TOWARD THE WEST-NORTHWEST OR 300 DEGREES AT 8 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 999 MBMAX SUSTAINED WINDS 30 KT WITH GUSTS TO 40 KT.WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICALMILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

REPEAT...CENTER LOCATED NEAR 19.2N 90.9W AT 27/2100ZAT 27/1800Z CENTER WAS LOCATED NEAR 18.9N 90.7W